Their nomadic lifestyle and ravenous raiding have taken army ants to most continents on Earth, but a rare fossil discovery is now offering first evidence that the notorious predator once swarmed a land they are strikingly absent from today.
The oldest army ant on record, preserved in Baltic amber, was discovered by researchers at New Jersey Institute of Technology and Colorado State University.
The Dissimulodorylus perseus is the second fossil army ant species and the first fossil recovered.
Researchers say the ant fossil brings to light previously unknown army ant lineages that would have existed across continental Europe before they died out.
The fossil was kept out of the public eye for over 100 years before being identified by the paper's lead author and NJIT graduate student Christine Sosiak.
The museum houses hundreds of drawers full of insect fossils, but I found a tiny specimen labeled as a common type of ant while gathering data for another project. I realized the label was incorrect when I put the ant under the microscope.
"This amber would have been excavated around or before the 1930s, so to now learn it contained a rare army ant is surprising," said Phillip Barden, assistant professor of biology at NJIT. There is no hint of extinct diversity in the army ants that live today.
There is a unique predator's history.
There are about 270 army ant species in the Eastern Hemisphere.
According to the NJIT team, D. perseus is a close relative of eyeless ants found in Africa and Southern Asia.
The ideal habitat for ancient army ants may have been found in Europe at the time of the fossil's creation. Europe underwent several cooling cycles over the course of tens of millions of years.
The team's analysis showed that the European army ant was similar to other army ants in its ability to survive underground.
This fossil and other fossil army ants are rare because of it. There was only one definitive fossil found until now.
This was a great find. "Because this ant was subterranean like most army ants today, it was less likely to come into contact with tree resin that forms such fossils." We have a small window into the history of life on our planet and fossils such as this provide fresh insight.
The specimen's pointed mandibles and lack of eyes help classify it as a worker ant, which would have been involved in raiding for food with soldier ants.
Army ants are involved in raiding swarms and hunting other insects. The army ants are blind and use chemical communication to coordinate their actions. "This worker may have deviated too far from its fellow hunters and into sticky tree resin which solidified and encased the ant as we see it today."
Army ants have a unique combination of behavior and trait that makes them deserving of their own name.
The army ants have wingless queens that are capable of laying millions of eggs a day, while their nomadic colonies temporarily occupy nest between phases of travel that take the shape of bivouacs.
The carnivores can consume upwards of 500,000 prey a day.
The army ant syndrome is a case of convergent evolution that happened twice in the Neotropics and once in the Afrotropics, according to Barden.
The army ant syndrome is the first evidence of it being in place before the ancestors of certain ant species.
There are just eight fossil species within the ant sub family that army ants belong to, and five of them are from Dominican amber.
The Museum of Comparative Zoology at Harvard University holds D. perseus.
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